The concurrent verbalization would affect not only the normal design behaviors but also the perceptual interactions between designers and their own sketches, while limited by short-term memory, video/audio retrospective protocols may probably induce some selective of memory trace and ambiguous verbal data, resulting in a lower accuracy of reports. This research focuses on examining the validity of video/audio retrospective and think aloud protocols, based on the qualitative comparison of the two methodologies. And we also want to understand the difference of the ability of collecting perceptual information between these two protocols. Moreover the segment and coding scheme for the drawings are primitively developed.